Optical fiber with a low-index core and a core grating
AssigneeCorning Incorporated
InventorsMing-Jun Li, Gaozhu Peng
Life of this patent
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Abstract
An optical fiber with a low-index core and a core grating has a solid and generally cylindrical annular cladding having a refractive index ncl, a central axis, an inner surface with a radius r wherein r≧2 μm, an outer surface with a radius R, and an annular thickness ΔR≧10 μm. The fiber core has the radius r and a refractive index nc, wherein ncl>nc. The grating is defined by grating elements that extend from the cladding inner surface into the core and that run generally parallel to the central axis. The grating elements define a period Λ, a width t, a spacing a and a height h, wherein 0.5<Λ/λ<1 and wherein 0.2≦t/a≦3.
Claims22
An optical fiber configured to guide light of an operating wavelength λ in at least one guided mode, comprising:
- a solid and generally cylindrical annular cladding having a refractive index ncl, a central axis, an inner surface with a radius r wherein r≧2 μm, an outer surface with a radius R and an annular thickness ΔR=R−r, wherein ΔR≧10 μm;
- a core disposed along the central axis and surrounded by the cladding, the core having the radius r and a refractive index nc, wherein ncl>nc;
- and
- a grating defined by grating elements that extend from the cladding inner surface into the core and that run generally parallel to the central axis, the grating elements defining a period Λ, a width t, a spacing a and a height h, wherein 0.5≦Λ/λ≦1 and wherein 0.2≦t/a≦3.
An optical fiber configured to guide light of an operating wavelength λ in at least one guided mode, comprising:
- a solid and generally cylindrical annular cladding having a refractive index ncl, a central axis, an inner surface with a radius r wherein 2 μm≦r≦200 μm and an outer surface with a radius R;
- a hollow core defined by the cladding inner surface, the hollow core having the radius r and a nominal refractive index nc=1, wherein ncl>nc;
- and
- a grating defined by grating elements that extend from the cladding inner surface into the core, the grating elements running longitudinally down the fiber and being generally parallel to the central axis, wherein the grating elements have a width t, a spacing a and a height h and define a grating period Λ=t+a, wherein 0.5≦Λ/λ≦1.
A method of forming an optical fiber configured to guide light of an operating wavelength λ in at least one guided mode, comprising:
- forming a bait rod having an outer surface with a first periodic grating formed therein;
- depositing a silica soot layer onto the outer surface of the bait rod to form a soot preform;
- consolidating the soot preform to form a glass preform, wherein the soot layer is converted to a glass layer and wherein the bait rod is disintegrated to form a hollow core in the glass preform, and wherein the glass layer has an inner surface with a second periodic-grating surface structure that is complementary to the first periodic-grating surface structure;
- and
- drawing the glass preform to form the optical fiber, wherein the optical fiber has the following properties:
- i) a solid and generally cylindrical annular cladding having a refractive index ncl, a central axis, an inner surface with a radius r wherein 2 μm≦r≦200 μm, an outer surface with a radius R and an annular thickness ΔR=R−r, wherein ΔR≧10 μm;
- ii) a hollow core defined by the cladding inner surface, the hollow core having the radius r and a nominal refractive index nc=1, wherein ncl>nc;
- and
- iii) a grating defined by grating elements that extend from the cladding inner surface into the core, the grating elements running longitudinally down the fiber and being generally parallel to the central axis, wherein the grating elements have a width t, a spacing a and a height h and define a grating period Λ=t+a, wherein 0.5≦Λ/λ≦1.
A method of forming an optical fiber configured to guide light of an operating wavelength λ in at least one guided mode, comprising:
- extruding a soot preform through an extrusion die that includes a first periodic-grating structure to define a hollow core with an inner surface that includes a second periodic surface grating complementary to the first periodic-grating structure;
- consolidating the extruded soot preform into a glass preform;
- and
- drawing the glass preform to form the optical fiber, wherein the optical fiber has the following properties:
- i) a solid and generally cylindrical annular cladding having a refractive index ncl, a central axis, an inner surface with a radius r wherein 2 μm≦r≦200 μm, an outer surface with a radius R and an annular thickness ΔR=R−r, wherein ΔR≧10 μm;
- ii) a hollow core defined by the cladding inner surface, the hollow core having the radius r and a nominal refractive index nc=1, wherein ncl>nc;
- and
- iii) a grating defined by grating elements that extend from the cladding inner surface into the core, the grating element running longitudinally down the fiber and being generally parallel to the central axis, wherein the grating elements have a width t, a spacing a and a height h and define a grating period Λ=t+a, wherein 0.5≦Λ/λ≦1.
Dependencies are inferred from the claim text.